<!DOCTYPE html>
<html lang="zh-cn">
    <head>
        <meta charset="UTF-8"/>
        <meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0" />
        <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
        <title>水平垂直居中-浮动方法</title>
        <style>
            .item {padding-top:30px;padding-bottom:30px;}
        </style>
    </head>
    <body>
        <div class="columns">
            <div class="item">test</div>
        </div>
    </body>
</html>